已知函数f(x)满足f(sinx)=cos2x,则f(cosπ/4)=

Question

已知函数f(x)满足f(sinx)=cos2x,则f(cosπ/4)=

Answer 1

设sinx=t
cos2x=1-2t^2
f(x)=1-2x^2
f(cosπ/4)= 1-2*(cosπ/4)^2
=1-2*(1/2)
=0